Surface Bacteria Inactivation by a DBD Plasma Sheet Generator

Non-thermal dielectric barrier discharge plasma finds its application in medicine, where it is used to inactivate bacteria on wound surfaces. In this paper, a dielectric barrier discharge plasma sheet generator was designed to replace the traditional plasma jet. The sheet generator is able to scan large surfaces as compared to a plasma jet. High purity helium was used as the working gas (~30-60 slpm), and the plasma was generated using an AC power supply (5-10kv, 10-30 kHz). The input plasma power was measured to be around a few Watts (~10-25W) depending on the operating conditions of the torch. An automated 2D traversing system was designed and used to scan the plasma sheet and measure plasma gas temperatures along the plasma sheet. Experimental results show that the temperature varies across the plasma sheet for up to 16 percent, and temperatures are more uniform near the exit of the plasma torch. The effectiveness of the plasma torch was determined by running it over agar plates in which E. coli K-12 bacteria was grown. An apparent reduction in the bacterial colonies (up to 44%) was observed as the plasma sheet was scanned along the petri dish for five minutes. The plasma sheet traverses a larger area, which is beneficial because it reduces the time taken by the plasma jet to cover the same area on the petri dish.